In performing ophthalmic extracapsular cataract surgery an opening must be provided in the anterior lens capsule of the eye through which the cataract is removed. This procedure involves the removal of the crystalline lens substance after opening or excising the anterior lens capsule.
Several methods have been utilized for opening the anterior lens capsule. An early method was needling or incising the membrane with multiple, slashing incisions made with a knife, needle or a scythe-like instrument called a cystotome. Another early technique involved grasping the anterior capsule with forceps and tearing off a piece of the capsule. A dull cystotome method has been utilized in which the anterior capsule is engaged opposite the entry site and is torn in one movement toward the surgeon, creating a triangular flap which is pulled out of the eye and then excised.
In recent years, many alternative capsulectomy methods have been proposed. Common to these methods has been the desire to increase the control of the excision with less emphasis on tearing and ripping. It is also recognized that endosurgical capsulectomy is desirable in order to visualize the capsule and avoid damage to adjacent intraocular tissue since the tissue which surrounds the endothelium of the cornea is sensitive to being touched, and the vision can be destroyed if the tissue around this space is traumatized. Thus, surgical instrumentation which is employed must be small in size. A technique widely utilized is known as the "can opener" method in which a hypodermic needle having its bevel bent to the shaft is used to make small triangular tears along the desired line of excision. The central piece of the anterior lens capsule is then grasped with a small forcep and is torn away along the perforations. However, since the anterior lens capsule is similar to a cellophane wrapping material, once a tear is initiated in an undesirable direction, the capsule may tear to the edge, resulting in a loss of structural stability of the membrane which often allows vitreous to spill into the anterior chamber.
Therefore, a need exists for a surgical instrument that allows for controlled incisions rather than unpredictable ripping or tearing and which allows the surgeon to obtain precise placement of the instrument for excision of the anterior lens capsule.